From Institute for Theoretical Physics II / University of Erlangen-Nuremberg

This page lists publications from the Marquardt group, in reverse chronological order. You may also
browse our research topics. We start with a few recent highlights. You find the reference list further below.

Coupled spin-light dynamics in cavity optomagnonics (Viola Kusminskiy, Tang, and Marquardt, 2016) - In optomagnonic cavities, light couples parametrically to magnons via the Faraday effect. This coupling was demonstrated very recently, in two experiments appearing at the end of 2015. In this article, we derive the microscopic Hamiltonian of the system and study the optically induced dynamics of a homogeneous magnon mode. We show that the system exhibits a plethora of nonlinear effects, such as chaos and self-sustained oscillations, which should be tunable and experimentally observable in current setups.

Sensing enhanced by de-amplification (Peano, Schwefel, Marquardt and Marquardt, 2015) - In this article we show that the precision of position detection can be enhanced by the squeezing generated internally in an optomechanical parametric amplifier. Counterintuitively, the enhancement of the signal-to-noise ratio works by deamplifying precisely the quadrature that is sensitive to the mechanical motion without losing quantum information.

Dynamical Gauge Fields in Optomechanics (Walter and Marquardt, 2015) - In this article we show that the most basic phonon-assisted photon tunneling process which is due to an optomechanical interaction leads to a scenario where phonons can act as a dynamical gauge field for photons, compared to previously studied static gauge fields. In the optomechanical setting these dynamical gauge fields arise in quite a natural manner. The mechanical oscillation phases determine the effective artificial magnetic field for the photons, and once these phases are allowed to evolve, they respond to the flow of photons in the structure.

Topological phases of sound and light (Peano, Brendel, Schmidt, Marquardt 2015) - A Phonon Chern insulator is formed when an optomechanical array is driven by a laser with an appropriate pattern of phases. The resulting chiral, topologically
protected phonon transport along the edges can be probed completely
optically. Moreover, we identify a regime of strong mixing between
photon and phonon excitations, which gives rise to a large set of
different topological phases. This work was also highlighted in Nature Photonics.

Optomechanical magnetic fields for photons (Schmidt et al. 2015) -
The optomechanical interaction between mechanical vibrations and light can be used to produce artificial magnetic fields for photons, in a tuneable way that is not tied to the geometry (as other approaches are) and is controlled entirely optically. This work was also highlighted in Nature Photonics.

Optomechanical Dirac Physics (Schmidt, Peano, Marquardt 2015) - Photonic crystals with many localized photonic and phononic modes could be used to form 'optomechanical arrays'. This paper predicts that engineering their optomechanical band structure gives access to many phenomena usually known in condensed matter. In particular, we predict optomechanical variants of the Dirac physics known from graphene, now affecting the transport of photon-phonon polaritons on a honeycomb lattice.

Optomechanical synchronization (Bagheri et al 2013) - In this experiment of the Tang group at Yale, two 'distant' nanomechanical resonators are coupled via the optical field inside a racetrack optical cavity. Their oscillations are observed to synchronize, which had previously been demonstrated only for disk resonators almost touching each other. In addition, novel features like peculiar sidebands in the observed mechanical spectrum show up. These hint at dynamics beyond the most widely used models of synchronization.

Where do the currents flow? (Kessler, Marquardt 2014) - In optical lattices, it is now experimentally possible to detect the precise location of single atoms. This paper suggests that this novel tool could also be used to take 'snapshots' of current patterns. These fluctuating patterns could reveal, via their statistics, important information about quantum many-body states of ultracold atoms, e.g. when an artificial magnetic field is applied.

Signatures of quantum nonlinearities (Kronwald, Marquardt 2013) - Optomechanical experiments are not yet able to observe indications of the nonlinear quantum nature of the optomechanical interaction. However, experiments are coming closer to this "nonlinear quantum regime". In this work, we propose a way how first indications of this nonlinear quantum regime could be observed in a two-tone driving experiment using near-future optomechanical devices.

Shuttling electrons, one by one (Moeckel et al. 2014) - Nanomechanical electron shuttles are little metallic islands that vibrate between electrodes, carrying electrons from one electrode to the other. In principle, they could be exploited to produce a precise current standard, essentially by counting the number of electrons. However, keeping track of the count is not so easy. In this paper, it is shown that the nonlinear dynamics of such a shuttle permits a trick: synchronization of self-oscillations to an external drive. This could drastically increase the precision.